This invention is generally directed to toner compositions, and the use of these compositions in electrostatographic imaging systems. More specifically, the present invention is directed to colored toner and developer compositions, containing therein certain organic charge enhancing additives, which impart a positive charge to the toner resin particles. Toner and developer compositions with the charge enhancing additives of the present invention are useful in various electrostatographic imaging systems, particularly colored imaging systems, having incorporated therein as the photoresponsive member a layered imaging device which is negatively charged.
Toner and developer compositions, including colored developer compositions are well known. These compositions usually contain toner particles consisting of a resin and colorants, and carrier particles. With regard to colored developer compositions the colorants are usually selected from cyan dyes or pigments, magenta dyes or pigments, yellow dyes or pigments, or mixtures thereof. There is thus disclosed in U.S. Pat. No. 3,844,815, colored developer compositions containing as the yellow pigment Foron yellow, while U.S. Pat. No. 4,035,310, discloses colored toner compositions containing as a yellow pigment Yellow 97, and carrier particles generally comprised of steel coated with various polymeric resinous substances.
Several prior art patents also disclose the incorporation into toner compositions as separate components, charge enhancing additives primarily for the purpose of imparting a positive charge to the toner resin particles. Ther is thus disclosed in U.S. Pat. No. 4,298,672 positively charged toner compositions containing resin particles, and pigment particles, and as a charge enhancing additive alkyl pyridinium compounds and their hydrates of the formula as detailed in Column 3, beginning at line 14. Examples of alkyl pyridinium compounds disclosed include cetyl pyridinium chloride. Moreover, there is disclosed in U.S. Pat. No. 4,338,390 positively charged toner compositions having incorporated therein as charge enhancing additives various organic sulfate and sulfonate compositions, including stearyl dimethyl phenethylammoniumpara-toluene sulfonate. Further, in U.S. Pat. No. 3,893,935 there is described the use of quaternary ammonium salts as charge control agents for electrostatic toner compositions. In accordance with the disclosure of this patent, certain quaternary ammonium salts, when incorporated into a toner material, provided a composition which exhibited relatively high uniform stable net toner charge when mixed with a suitable carrier vehicle; which toner also exhibited a minimum amount of toner throw off.
Additionally there is disclosed in the prior art colored toner and developer compositions containing as charge enhancing additives para-halophenylcarboxylic acids, and the salts thereof. More specifically, there is disclosed in this patent positively charged toner compositions containing resin particles, dye particles, such as cyan, magenta, or yellow dyes, and as a charge enhancing additive, in an amount of from about 0.1 percent by weight to about 10 percent by weight, para-halophenylcarboxylic acids, and the salts thereof, including 4-fluorobenzoic acid, 4-chlorobenzoic acid, and 4-bromobenzoic acid.
While the above described toner and developer compositions are suitable for their intended purposes there continues to be a need for new developer compositions. Specifically there continues to be a need for colored toner compositions wherein a charge establishing group is desirably coupled to a chromophore or colorant, thereby providing anchoring by covalent bonding, allowing the resulting high molecular weight compounds to retain the charge establishing group therein. In contrast with many of the prior art charge enhancing additives they in many instances are undesirably leached from the toner composition, and thus must be continously monitored and replaced. Furthermore there remains a need for colored toner compositions wherein the charge establishing additive can be varied as desired depending on the colorant chromophore selected, and the triboelectric charge value to be imparted to the toner resin particles. Additionally there continues to be a need for colored toner compositions wherein the combined chromophore charge establishing group molecule is water insoluble, and therefore evidences reduced humidity sensitivity allowing the resulting triboelectric charge values imparted to the toner resins to be maintained at a relatively constant level. Further there remains a need for colored toner compositions in which dyes rather than pigments are employed as the colorants, thus imparting greater clarity and brightness to the resultant electrographic prints. There is also a need for dye colorants that are highly compatible with their host resinous material, and evidence substantially no tendency to leach, bleed, or sublime from the host resin.